Cutoff switch for screw feeders



Gct. 26,1948. v c. J. st|-|E.'| n |r-n:s` 2,452,395

A l GUTOFF SWITCH' FOR SCREW FEEDERS Filed July 9, 1946 l LINE INVENTOR.. v 4 Clarence, Schelm? -ery of heat into the boiler.

Patented Oct. 26, 1948 UNITEDv STATES PATENT OFFICE 2,452,395 CUTOFF SWITCH FOR SCREW FEEDERS Clarence Joseph Schelling, Chicago, Ill.

Application July 9, 1946, Serial No. 682,197

4 claims. l

This invention pertains to a new and improved type of a control that cuts off power whenever the supply in the conveyor system is too low. It is more particularly adapted in connection with stokers and similar devices which have a worm type of conveyor feeding the fuel to the retort.

Ordinary stoker and like devices have a number of controls operating in connection therewith. Most of these are controlled by temperature or pressure within the boiler, pipes, returns or temperature within the building. Also to maintain re particularly under mild weather conditions where stoker is not in frequent use, an additional control to automatically place the burner into operation and maintain it for a short interval of time is also provided. All of these devices are provided so that the stoker can be held in readiness when the temperatures drop and the need for heat becomes urgent within the dwelling.

However, a stoker requires fuel to function and maintains stability of operation and deliv- In practice, the maintenance engineer charges the bin of the Stoker with properly sized coal about his other important duties. At times when an unusual demand for heat must be met and in the absence of the maintenance engineer, the fuel stoker bin will empty and consequently the fire will burn itself out in the retort.

Besides the above disadvantage, some types of stokers using sized coal may have a tendency to form clinkers and fuse within the fire retort within the furnace of the heating means. Again, as the fuel in the worm tube becomes exhausted more and more air is forced into the retort while the coal is rapidly being diminished and there is a tendency to overheat the retort linings. Consequently, in time and under such repeated action they will burn out.

It likewise is obvious that when the coal is consumed, that the various controlling devices such as thermostats, aquastats, timers, etc., will all call for heat. Because there is this request, the stoker will continue to work and force cold air into the retort and linings of the furnace. This cold air will chill rapidly the retort andthe furnace linings, cause shrinkage cracks and set up other undesirable strains and stresses within the heating equipment. All of these exert a deleterious effect upon the equipment and have a tendency to shorten its life. In addition, the cold air supplied by the blower of the stoker instead of retaining heat within the heater, re-

and then goes4 moves it since it chills I heater and forces this air into the'chimney.

It, therefore, is an object of this invention to provide a means whereby a Stoker can be automatically shut 01T in case the fuel supply shall fail.

It is a further object of this invention to provide a means which will indicate that the stoker is shut oi and that fuel is needed.

A still further object of this invention is to provide a means that will automatically cut ofi the blower on the stoker if the fuel supply shall fail and to protect and prolong the life of the burning equipment.

These and other objects, extensions, variations, modifications, and adaptations will become apparent to one skilled in this art particularly in light of the clear, lucid and'accurate description given below of the fundamental principles underlying my invention.

For a more fuller understanding of my invention, reference should also be had to the accompanying drawing annexed hereto and forming a part of this specification. For clarity, the reference numerals in the drawings designate the same parts described in the specification.

Figure l shows schematically a heating unit, the fuel worm conveyor tube, with the cut oi and stoker mechanism with the fuel bin partly cut.

Figure 2 shows sectionally and in detail the means used in actuating the low fuel cutoif switch, the assembly and also diagrammatically the electrical circuit.

In a boiler ID or other heating means where a stoker is installed,a retort l2 consisting generally of an alloy capable of withstanding high temperatures is placed in the center within the furnace ll. It rests upon a tuyre box I4 where the fuel and air (both not shown) are blended together and fed vertically into the retort l2 where the combusion takes place. Many stokers have preferably an auxiliary tube (not shown) for conveying air from the blower enclosed in 'the housing 26 to the retort l2, but for sake of simplicity and since it is not a part of my invention, I have omitted showing it. Nevertheless, it will be obvious that my invention can be readily used with either type and therefore it is not intended to limit its application.

The fuel or coal is placed in the hopper 28 from where it is conveyed by a worm screw l1 thru the tube housing i8 and the extension thereof IS into the tuyre box l and finally into the combustion retort l2.

the heated waus of me Adjacent the motor and blower housing 28,.and

mounted on the worm screw housing I8 is the low fuel cutoff 28 and its reset button 22.

The low fuel cutoff housing 20 consists of a rectangular box consisting of a lower section 30 and an upper section 32. A divider or dust gasket 34 divides the box into two sections. The upper section 32 containsthe electrical connections. It is designed and constructed to be dustproof and to prevent the infiltration of coal dust. As an additional safety precaution, a switch 33 of the totally enclosed contact type known also as a mercury contact switch is suitably mounted on the divider plate 34. An arm 38 which is an extension of the switch 36 is supported in an upwardly sustained position by spring 48. A trip arm 42 is suitably mounted on the upright rod 44 which extends upwardly thru the cover plate 46 and terminates into the reset button head 22. Suitable screws 48 firmly attach the plate 46 to the upper part of the housing 32. An insulative bushing 58 provides entry for vthe electrical wires 82 to lead 4 60 falls into the interior of the tube. The upright rod 44 attached pivotedly to the heel 83 is pulled downwardly until the arms 42 and 38 trip the mercury switch 38 and open the circuit to stop the motor.

When the fuel is replaced or if the operator desires to set the switch, the button 2? is raised and the mercury switch 3B again closes the circuit to start the screw conveyor into motion. When the screw tube I8 becomes filled with coal. the heel plate 60 is pressed against the detent 10. As long as it is held in this position, the operation of the circuit is not interfered with.

from the mercury contact switch 38 to the control circuit.

The upper section 32, the lower section of the housing 20 and the divider plate 34 are held together with nuts and bolts 54 and 56. A seal 58 of rubber, leather or some other suitable material is provided about the upright rod 44 to prevent coal dust from creeping into the electrical contact chamber 32.

The lower part of the upright reset button rod 44 terminates in a pivot 59 which is attached to a heel 60. 'Ihe heel B0 is a movable plate forming a part of the wall of the tube I8 which houses the screw I 1 that conveys the coal or other material from the hopper to another place. At one end thereof is an arm 6I thru which are bored two holes 62 and 64. A rib 66 extending from the wall of the lower section 30 of the housing is also provided to act as a bearing support for the pin B8 which acts as a pivot axis 68 for the heel 6I). Coal or other material in the tube under the inuence of the conveying screw I1 will force upwardly the heel 68 about the pivot point 68 until the other end of the heel B0 contacts the detent nib l0. This nib I0 prevents the heel 80 from further opening and thus retains the fuel within the tube I8. To prevent the heel from falling into the tube and injuring the screw I1 in case there is no fuel, a thumb set screw 14 extends thru the wall of the housing 38, thru the opening 64 of the arm 6I and terminates in a lock 18 that prevents the arm 6I from lowering the heel plate B0 into the path of the screw I1. A lock nut 18 maintains the set screw 14 in a fixed position. To prevent the heel IIi from sticking a coil spring 80 is inserted between the divider plate 34 and the top of the heel plate 60 to spread apart the plate from the detent 10. The lower section 30 of the housing 28 is welded to the tube housing I8.

If for some reason the supply of the material conveyed in the tube I8 fails then the heel plate The circuit shown is only one of the many that are possible and obviously can readily be improvised by one skilled in this art without departing from the principles underlying my invention.

Though the above example described in detail is given purely for illustrative purposes and should not be construed or even intended to be a limitation of the principles underlying my invention for manifestly they can be varied widely and stili be within the scope of the spirit of my invention as donned hereinbelow in the appended claims.

I claim:

l. In combination with a stoker fuel feed assembly comprising a screw conveyor tube, a housing attached to the said screw conveyor tube, a divider in said housing to form therein two chambers. the floor of the lower chamber pivotally mounted to said housing and responsive to the pressure of flow of fuel in said screw conveyor tube, means in said lower chamber to limit rise and fall of said pivoted oor, a rod pivotally mounted on said movable floor, the said rod extending thru the said divider, the upper chamber and terminating above said housing, a trip arm attached to the rod portion within the upper chamber and a means in contact with said arm to make and break an electrical circuit actuating the motive power whereby the fuel feed is stopped when there is no pressure in said conveyor tube.

2. In the combination of claim l, wherein the said pressure responsive pivoted oor is of the same contour as said conveyor tube.

3. In the combination of claim 1, wherein the said means for controlling the rise and fail of said plate consists of a thumb set lock bolt inserted respectively thru the wall of the lower housing sectionand an arm extension pivoted about its lower end.

4. In the combination of claim l, wherein the said upper chamber is of a dustproof construction.

CLARENCE JOSEPH SCHELLING.

REFERENCES CITED UNITED STATES PATENTS Name Date Justus Oct. l, 1935 Number 

